Somervile Mayor Joseph Curtatone and School Superintendent the poem in Kim Conley's class is an example of "how one of our educators used a rhyme to help her young students stay calm and remember the key steps they would need to follow during a drill or real emergency."

"As much as we would prefer that school lockdowns not be a part of the educational experience, unfortunately this is the world we live in," they said in a statement to CNN. "It is jarring -- it's jarring for students, for educators, and for families."

The painful feelings it brings up

Go behind the desk and hide

Wait until it's safe inside

Healey said reading the poem reminded him of the shooting at Marjory Stoneman Douglas High School -- his alma mater and the target of a February 14 shooting that left 17 dead and several others wounded.

Seeing the lyrics brought up "difficult, negative feelings," he said.

Since 2009, the US has seen 57 times as many school shootings as six other industrialized nations combined.

The fear is so pervasive that last month, students around the nation shared a hashtag "#IfIDieInASchoolShooting, offering a woeful glimpse into the sense of apparent inevitability that someday soon, they'll be felled by bullets on campus.

This is the new normal

A few weeks ago, Cohen said their daughter came home, excited to share a fun game she played with her pre-K class: try to stay quiet for one whole minute, just like during a lockdown.

"This shouldn't be something that we get used to," Cohen said. "We need to keep being jarred, upset and shook."

As Healey and Cohen talked to CNN, their daughter was cheerfully playing with Legos, unaware of how conversations of guns, shootings, lockdowns and fear have become so commonplace.